11.The 11th term and the 21st term of an A.P. are 16 and 29 respectively. Find1.the 1st term and the common differenceii.the 34th termiii.'n' such that tn = 55.
Question
11.The 11th term and the 21st term of an A.P. are 16 and 29 respectively. Find1.the 1st term and the common differenceii.the 34th termiii.'n' such that tn = 55.
Solution
i. To find the first term (a) and the common difference (d) of an arithmetic progression (A.P.), we can use the formula for the nth term of an A.P., which is a + (n-1)d.
Given that the 11th term is 16 and the 21st term is 29, we can set up the following two equations:
16 = a + 10d (equation 1) 29 = a + 20d (equation 2)
Subtracting equation 1 from equation 2 gives us:
13 = 10d
So, d = 1.3
Substituting d = 1.3 into equation 1 gives us:
16 = a + 10(1.3) 16 = a + 13 a = 16 - 13 a = 3
ii. To find the 34th term, we can use the formula for the nth term of an A.P.:
Tn = a + (n-1)d T34 = 3 + (34-1)(1.3) T34 = 3 + 33(1.3) T34 = 3 + 42.9 T34 = 45.9
iii. To find 'n' such that Tn = 55, we can set up the following equation and solve for n:
55 = 3 + (n-1)(1.3) 52 = (n-1)(1.3) n-1 = 52/1.3 n-1 = 40 n = 41
So, the 1st term and the common difference are 3 and 1.3 respectively, the 34th term is 45.9, and 'n' such that Tn = 55 is 41.
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